• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.213-213
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• 2012

We first confirm the tautomerization of 2-thiazoline-2-thiol on Ge (100) surface using CLPES and DFT calculation. We clearly confirmed that there exist two different molecular structures (we well show in our poster) in C 1s, N 1s, and S 2p CLPES spectra. Moreover, we obtained two plausible adsorption structures using DFT calculation which are that one is s-dative bonded structure and the other is SH dissociated-N-dative bonded structure although their stabilities are different on Ge (100) surface. We will investigate this interesting result for the confirmation of tautomerization of 2-thiazoline-2-thiol molecule adsorbed on Ge (100) surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.644-647
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• 2001

Amorphous As-Ge-Se-S thin films have been studied with the aim of identifying optimum etching condition which can be used to produce holographic grating structure for use as diffractive optical elements. In this study, holographic gratings have been formed using He-Ne laser(632.8nm), and fabricated by the method of wet etching using NaOH etchant with various concentration(0.26N, 0.33N, 0.40N). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. The formed grating profiles were observed by atomic force microscope and showed that the expected grating profile could be achieved by controlling the etching time. Over-etching resulted in under-cutting of the grating lines. The highest 1st order diffraction efficiency for these gratings was about 5.05%.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권9호
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• pp.423-428
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• 2006

We have been carried out the two-beam interference method to form the diffraction grating on chalcogenide $AS_{40}Se_{15}S_{35}Ge_{10}$ thin films for Holography Data Storage (HDS). In the present work, we have been formed holographic diffraction gratings using He-Ne laser (632.8nm) under different Polarization state combinations (intensity polarization holography, phase polarization holography). It was obtained the diffraction grating efficiency by 11st order intensity and investigated the formed grating structure using Atomic Force Microscopy (AFM). As the results, it is shown that the diffraction efficiency of (P: P) polarized recording was maximum 2.4% and we found that its value was rather higher than that of other-polarized recordings. From the results, it is confirmed that the efficient holographic grating formation on amorphous chalcogenide $AS_{40}Se_{15}S_{35}Ge_{10}$ films depend on both the spatial variation of intensity and the polarization state of the incident field pattern.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권7호
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• pp.354-358
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• 2006

In this paper, we investigated the selective etching rate of amorphous As-Ge-Se-S thin film due to the photoexpansion effect and fabricated the 2-dimensional embossing type diffraction grating hologram. We measured the thickness change with the etching time among NaOH solution after forming 1-dimension diffraction grating. As a results, we found that the selective etching rate were $2.5\AA/s,\;3.3\AA/s,\;3.9\AA/s$ where NaOH solution concentration were 0.26N, 0.33N, 0.36N, respectively. Also after the formation of 2-dimensional diffraction grating by the $90^{\circ}$ degree of circulation on the formed 1-dimensional diffraction grating, we etched selectively during 60sec, among 0.26N NaOH solution and obtained 2-dimensional embossing diffraction grating. As the results of AFM (Atomic Force Microscopy), we confirmed the formation of distinct embossing type 2-dimensional diffraction grating hologram, successfully.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.490-493
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• 2003

We have carried out two-beam interference experiment to form holographic grating on amorphous $As_{40}Ge_{10}Se_{15}S_{35}/Ag$ double-layer. In this study holographic grating formed using He-Ne laser(632.8nm) under non-polarization state and p-polarization state and we confirm that the diffraction efficiency depend on thickness of Ag. The diffraction efficiency was obtained by first order intensity. We got the maximum diffraction efficiency that thickness of Ag was $600{\AA}$. The maximum diffraction efficiency was 13.5% in (P:P) polarization state.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.590-593
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• 2004

본 논문에서는 $As_{40}Ge_{10}Se_{15}S_{35}$ (300nm)박막과 $As_{40}Ge_{10}Se_{15}S_{35}$ (300nm)/Ag(20nm)박막에 홀로그래피 격자를 형성시킨 후 Tg 온도$(240^{\circ}C)$를 기준으로 하여 유리질 천이온도(Tg) 온도 이하 $(190^{\circ}C)$와 이상$(270^{\circ}C)$에서 열처리 시킨 후의 회절효율 변화를 알아보았다. $As_{40}Ge_{10}Se_{15}S_{35}$ (300nm) 박막의 경우 $190^{\circ}C$ : 50%, $240^{\circ}C$ : 약80%, $270^{\circ}C$ : 약 98%의 회절효율 감소가 일어났으며 $As_{40}Ge_{10}Se_{15}S_{35}$(300nm)/Ag(20nm)박막에서는 Tg 온도 이하 즉 $190^{\circ}C$, $240^{\circ}C$ 에서는 회절효율의 변화가 없었으나 Tg온도 이상인 $270^{\circ}C$에서는 약 1.5배 증가한 회절효율을 나타내었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권8호
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• pp.387-391
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• 2006

The Ag photodoping effect in amorphous $As_{40}Ge_{10}Se_{15}S_{35}$ chalcogenide thin films for holographic recording has been investigated using a He-Ne laser (${\lambda}$=632.8 nm). The chalcogenide films thickness prepared in the present work were thinner in comparison with the penetration depth of recording light ($d_p=1.66{\mu}m$). It exhibits a tendency of the variation of the diffraction efficiency (${\eta}$) in amorphous chalcogende films, independently of the Ag photodoping. That is, ${\eta}$ increases rapidly at the beginning of the recording process and reaches the maximum (${\eta}_{max}$) and slowly decreases slowly with the exposed time. In addition, the value of ${\eta}_{max}$ depends strongly on chalcogenide film thickness(d) and its maximum peak among the films with d = 40, 80, 150, 300, and 633 nm is observed 0.083% at d = 150 nm (approximately 1/2 ${\Delta}n$), where ${\Delta}$n is the refractive index of chalcogenide thin film (${\Delta}n=2.0$). The ${\eta}$ is largely enhanced by Ag photodoping into the chakogenides. In particular, the value of ${\eta}_{max}$ in a bilayer of 10-nm-thick Ag/150-nm-thick $As_{40}Ge_{10}Se_{15}S_{35}$ film is about 1.6%, which corresponds to ${\sim}20$ times larger than that of the single-layer $As_{40}Ge_{10}Se_{15}S_{35}$ thin film (without Ag). And we obtained the diffraction pattern according to the formation of (P:P) polarization holographic grating using Mask pattern and SLM.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.63-63
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• 2011

비정질 반도체/절연체의 직류와 교류 전도도 스펙트럼은 주파수에 대한 거듭제곱의 법칙 (power-law)을 따르는 보편성이 있음이 확인되었다. 이러한 보편성은 다양한 비정질 반도체/절연체 물질에서 공통적으로 관찰되었으며 현재까지 이 보편성의 물리학적 원인이 정확히 규명되지 않고 있다. 이 보편성을 설명하기 위한 모델로서 비정질 반도체/절연체 내의 전자/정공의 호핑 전도기구 (hopping conduction mechanism)가 제시된 바 있으며 다양한 비정질 시스템의 전도도 스펙트럼 해석에 인용되고 있다. 그러나 직.교류 전도기구 사이의 상이함에 대한 이견이 있으며 현재까지 정확히 규명된 바 없다. 본 연구에서는 비정질 GeSe 반도성 물질의 전도도 스펙트럼을 10 Hz-1 MHz 주파수 대역에서 측정하였으며 이를 위해 백금 상.하부 전극을 갖는 크로스바(crossbar)형의 금속-절연체-금속구조의 2단자 소자를 제작하였다. 측정 스펙트럼으로부터 본 연구의 GeSe 물질이 앞서 언급한 비정질 물질의 보편성에 부합함을 확인하였으며 스펙트럼 내의 직류와 교류 성분을 명확히 분리할 수 있었다. 직.교류 전도도 스펙트럼의 명확한 기구 분리를 위하여 4개의 상이한 면적을 갖는 크로스바에 대한 측정을 실시하였으며 그 결과로 직.교류 전도도의 상이한 면적 의존성을 관찰하였고 이를 근거로 직.교류 전도도가 서로 다른 전도기구에 기인함을 간접적으로 알 수 있었다. GeSe의 전도도 스펙트럼의 온도 의존성 실험을 위해 시편의 온도를 20-300 K 범위에서 변화시키며 전도도 스펙트럼을 측정하였으며 이를 통해 교류 전도도 스펙트럼 내에 상이한 두 개의 전도 기구가 혼재해있음을 규명하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.237.2-237.2
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• 2013

ReRAM cell, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of conductive filament in a solid electrolyte [1,2]. Especially, Chalcogenide-based ReRAM have become a promising candidate due to the simple structure, high density and low power operation than other types of ReRAM but the uniformity of switching parameter is undesirable. It is because diffusion of ions from anode to cathode in solid electrolyte layer is random [3]. That is to say, the formation of conductive filament is not go through the same paths in each switching cycle which is one of the major obstacles for performance improvement of ReRAM devices. Therefore, to control of nonuniform conductive filament formation is a key point to achieve a high performance ReRAM. In this paper, we demonstrated the enhanced repeatable bipolar resistive switching memory characteristics by spreading the Ag nanocrystals (Ag NCs) on amorphous GeSe layer compared to the conventional Ag/GeSe/Pt structure without Ag NCs. The Ag NCs and Ag top electrode act as a metal supply source of our devices. Excellent resistive switching memory characteristics were obtained and improvement of voltage distribution was achieved from the Al/Ag NCs/GeSe/Pt structure. At the same time, a stable DC endurance (>100 cycles) and an excellent data retention (>104 sec) properties was found from the Al/Ag NCs/GeSe/ Pt structured ReRAMs.

• 한국광학회지
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• 제14권6호
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• pp.594-599
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• 2003

1.6 $\mu\textrm{m}$ 파장대의 U밴드 광증폭기용 광섬유 소재인 Pr첨가 Ge-Sb-Se 계열 셀레나이드 유리의 굴절률을 분광타원법을 이용하여 결정하였다. 시료의 광물성을 조사하기 위해 투과 파장 영역에서의 타원 스펙트럼을 Sellmeier 분산관계식에 기반한 공기/미시 거칠기층/표면층/기층으로 구성된 4상계의 모델에 적용하여 굴절률과 분산계수 및 박막구조상수를 동시에 얻을 수 있었다. 디스크 형태로 가공된 각 시료의 양면을 대상으로 위치에 따라 수회 반복 측정을 통하여 시료의 표면 거칠기의 영향을 파악함으로써 조성 변화에 대한 굴절률 변화 양상을 보다 정확히 파악하였다. 시료의 표면 거칠기가 굴절률 측정치의 편차에 주된 영향을 미쳤으나 1 몰%에 해당하는 소량의 조성변화에 따른 굴절률 변화를 신뢰할 수 있는 수준으로 결정할 수 있었다. 실험적으로 결정된 조성변화와 굴절률과의 관계식은 단일모드의 셀레나이드 광섬유 제작에 있어 코어와 클래드의 조성을 결정하는데 직접적으로 활용될 수 있다.